In checking out some of the news this morning, I noticed the following as one of the ABC’s main headlines:

Petrol rise to limit emissions unsustainable: economist

Before I go on, I think it’s worth explaining how I interpret this headline, and why. The noun phrase petrol rise need not refer to a policy decision to raise petrol; it may simply be a matter-of-fact observation that the price of petrol is increasing. But the embedded verb phrase to limit emissions makes the volitional interpretation clear; the price of petrol is being raised for a purpose; to limit emissions.

Moreover, the predicate unsustainable confirms this, as sustainability is a characteristic usually attributed to something over which someone, at least somewhere, has some control. You can talk about (un)sustainable economic growth, (un)sustainable agriculture, but you can’t really talk about (un)sustainable reptilian skin shedding. The reason for this, I’d contend, is that sustain is an ergative1 verb; it requires a volitional agent as much as murder does.

Okay, that said, I can talk about the more interesting pragmatic aspects of this headline. As far as I’m aware, there is no policy to raise the price of petrol in order to limit carbon emissions. In fact both government and opposition plan to lower the price of petrol instead of doing anything proactive to mitigate justifiably high fuel costs.

So why the headline? It seems to me to imply that there is currently a policy, to raise petrol prices, that would be unsustainable.

I think the ABC are violating one of the key Gricean maxims of conversational implicature. The ABC has not been as informative with this headline as required by the context. Further on in the article however, we find more information:

[The economist advising the Federal Government, Ross Garnaut] has rejected any notion that petrol should be exempt from a future carbon emissions trading scheme and suggested higher petrol prices could help mitigate carbon emissions.

But Professor Garnaut says in the long term, hiking petrol prices to control emissions is unsustainable.

So the fact that Garnaut warned about prolonged petrol price rises is in fact meant to be taken in the context of his suggestion to raise them in the first place. This, I believe, is a violation of the maxim of quantity; the reader is not given enough information in the headline to know the context in which Garnaut is warning us about prolonged petrol price rises. Also, since we’re told about the warning without the context behind it, this is also arguably an example of the converse of this maxim; we’re told too much information than is required by the circumstances.

A much more conversationally optimal headline, in my humble opinion, would have been something along the lines of Raise petrol prices to limit emissions: economist.

For want of a better term. I don’t want to use traditional terms like ‘active verb’, but I think you get the idea.